2. There's someone who knows how to use it to shock your heart back into rhythm and do cardiopulmonary resuscitation
(CPR) to keep a trickle of oxygenated blood flowing to your brain.

3. When they turn on that defibrillator, the battery isn't dead and the paddles aren't out of date.

But that last one, it turns out, is a big "if." A recent report in Spectrum, the magazine of the Institute of
Electrical and Electronics Engineers, found that failures of public-use defibrillators -- the ones in your local
shopping mall, gym and workplace -- increased by 85 percent over a five-year period. There was one malfunction for every
50 devices in the country, and more than 750 of the 28,000 failures involved a death. (Read more about the study
here.)

Why Defibrillators Don't Always Work

Many of those AEDs -- automated external defibrillators -- are victims of neglect. When no one is in charge of checking
batteries and keeping parts up-to-date, they're left to gather dust. And when they're needed, they're DOA (dead on arrival).

"I've been places where I've been told proudly, 'We have an AED,' and I say, 'Yes, but your AED is dead and the pads
expired months -- if not years -- ago,'" says paramedic Jonathan Epstein, executive director of NorthEast Emergency
Services Inc./Massachusetts Region III EMS Council and member of the American Red Cross Scientific Advisory Council.

As part of his job, Epstein advises clients on emergency response procedures, which includes AED upkeep, training, and oversight. "In a public place like a workplace, at least 10 percent of the staff should be trained in AED use and CPR. More than one person in a household should be trained in CPR."

But there's good news. Every year, 5 million people sign up with the American Red Cross to learn CPR and how to operate an AED. And AEDs do work -- as long as someone is taking care of them.

Epstein has seen what can happen when those stars are aligned. "In one workplace about a month ago, a worker collapsed. His co-workers started CPR and had a defibrillator on his chest in less than a minute. He was clinically dead. But with good CPR and good AED on top of it, he was back to work a week and a half later."

Life-saving Skills You Need to Know

Don't think that cardiac arrest is rare. It happens to as many as 450,000 people, including children, every year in the US. That's one every 1.5 minutes. Sudden cardiac arrests cause more deaths than stroke, breast cancer and lung cancer combined.

"You have about a six-minute window to get someone's heart started again," says Dr. Mickey Eisenberg, professor of medicine at the University of Washington and medical director of the King County Emergency Medical Services in Washington State. "That becomes 10-12 minutes if CPR is started right away. CPR will not convert a heart to a normal rhythm, but it buys time."

When I learned CPR about 30 years ago, it was not for the squeamish. Then, you had to do mouth-to-mouth as well as the hard-and-fast chest compressions. My instructor felt it necessary to warn us that sometimes a resuscitated victim can vomit and you don't always have time to get out of the way. I prayed -- for many reasons -- that I'd never have to use it.

Why CPR Is Easier Than Ever

But today, says Eisenberg, mouth-to-mouth is no longer part of the training. "Only firefighters and paramedics have to learn the full deal," he says. Hands-only CPR is so easy to do, says Epstein, the Red Cross teaches it in its babysitter classes to kids as young as 12. "My own daughter could do it when she was 9," he says.

While the experts encourage everyone to get certified, which means taking a four-hour class (find one here), the truth is that anyone can do CPR with a little coaching. "If you call 911, the dispatcher can tell you what to do," says Eisenberg.

AEDs are equally dummy-proof. "The key thing is to turn it on," says Epstein. "It tells you where to put the pad and what steps to take."

You can also bone up on the procedure on Eisenberg's website where he offers illustrated guides to CPR techniques for adults, children, infants and even cats and dogs. Also on his site: a link to two free iPhone and Android apps with videos you can watch and follow when an emergency strikes.

If all else fails, just remember two words: hard and fast.

"If someone's heart has stopped, you need to press the chest 100 times per minute and go 2 inches down," says
Eisenberg. "Now, it sounds gruesome, but you may hear cracking sounds. That's cartilage breaking in the chest. It can be
scary. You may think you're harming the person. But consider the alternative. That person is clinically dead at that
moment. You cannot do them harm. Clinical death will become biological death within eight minutes, so you have to jump
in fast."